1. Field of the Invention
The invention relates generally to textile ring spinning or ring twisting frames having winding units with rotatably mounted thread follower rings, particularly to a method and apparatus for restarting an individual winding unit of such a frame without slowing or stopping the other winding units of the frame.
2. Description of the Prior Art
Rotatably mounted rings, as compared to nonrotatably mounted rings, are advantageous in that they allow operation of the spindles at considerably higher speeds and thus increased production.
This is especially true for air cushioned rings. The invention therefore relates especially to air cushioned rings including both aerostatic and aerodynamically mounted rings. In the case of aerostatic bearings, the bearing is acted upon by externally supplied air, whereas in the case of aerodynamic bearings, the air cushion is formed by the auto-rotation of the rotatable part of the bearing.
In such machines, a problem that hitherto has not been solved satisfactory is that of how to bring the pertinent winding units again up to the operational speed after a thread break without danger of a new thread break or damage of the ring. In these machines, normally all spindles, or at least the spindles on one longitudinal side of the machine, are driven in common by a tangential belt or by small belts driven jointly be a single drum. Thus, any spindle, which has been stopped either by hand or by means of a spindle brake for the purpose of correcting a thread break upon being released, will accelerate quickly to its operational speed which, at least in the case of air cushioned rings, is so high that the traveler dragged by the thread revolves on the ring at an impermissibly high speed relative to the ring. Consequently, the traveler can wear down extremely quickly and break and the traveler path of the ring can be damaged, or the thread can break as a result of too high a thread tension. Even though the traveler drives the ring, the ring is accelerated only relatively slowly by the traveler and thus will reach its high operational speed relatively slowly, whereas the traveler will reach a very high speed relatively quickly since it is driven directly by the spindle by way of the thread. In most instances, the speed of the traveler is only relatively slightly lower than the speed of the spindle. For example, with air cushioned rings, one can achieve spindle speeds of 20 000 rpms and more, so that the traveler at such high rpms is exposed to extremely great centrifugal forces and, because of the slow acceleration of the ring, will rotate for a relatively long time at impermissibly high speeds. Even for air cushioned rings, the relative speed between the traveler and the ring must not be essentially higher than that of non-rotatably disposed rings so that, for example, only relative rpms of 8000-12 000 rpms are permissible.
Whenever the entire ring spinning or twisting machine accelerates from standstill, then the problem of acceleration had been solved by allowing the machine to accelerate to its operational speed only relatively slowly so that no impermissibly high relative rpms occurred between the travelers and the rings. But, whenever during the subsequent standard operation, thread breaks on individual spinning or twisting positions are to be eliminated, the entire machine could be stopped per se before restart of the particular winding unit or it could be allowed to run more slowly. However, in view of the large number of spinning and twisting units which such machines have, either stopping or operating the machine at a reduced speed during the repair of each and every thread break could cause a high loss of production. Until now, the only alternative left was to delay the repair of the thread breaks until the end of the pertinent pull off on the spinning and twisting units where thread breaks occurred; as a result the pertinent spinning or twisting units were eliminated for the further production during this pull off, which naturally is likewise very disadvantageous.